Virtual studio systems have made the transition from experimental prototypes to commercial products used for regular broadcast production. This article covers the history of virtual studio development, from early experiments in extending traditional chromakeying to current systems based on graphics supercomputers. Topics treated include the key components needed for tracking, rendering, and compositing. The article discusses basic techniques in such areas as lighting and camera calibration, and describes advanced features such as video textures, Z-keying, and virtual actors. The authors also survey current commercial systems, discuss various extensions and alternative approaches, and mention some of the issues facing broadcasters who introduce virtual studio systems.